1. Technical Field
The present invention relates to a liquid ejecting head and a liquid ejecting apparatus, and to a piezoelectric element.
2. Related Art
Ink jet recording heads are a typical type of liquid ejecting head. An ink jet recording head includes a vibration plate defining a part of a pressure generating chamber communicating with a nozzle aperture through which ink droplets are ejected. In the ink jet recording head, a piezoelectric element vibrates to deform the vibration plate so as to apply a pressure to the ink in the pressure generating chamber, thereby ejecting ink droplets through the nozzle aperture. Some of the piezoelectric elements used in ink jet recording heads comprises a piezoelectric layer and two electrodes. The piezoelectric layer is made of a piezoelectric material with electromechanical conversion. Two electrodes are on two sides of the piezoelectric layer. This type of piezoelectric element is used as a deflection vibration mode actuator device of a liquid ejecting head.
JP-A-2001-223404 discloses a liquid ejecting head using lead zirconate titanate (PZT) having a high displacement property as the piezoelectric ceramic. However, liquid ejecting heads using piezoelectric ceramics in which the content of lead, which is a toxic substance, is reduced are desired from the viewpoint of environmental protection. It is known that (K,Na)NbO3 materials, called as KNN are important lead-free piezoelectric ceramics having a ABO3 perovskite structure and containing potassium, sodium and niobium, as its main composition (for example, JP-A-2008-50206).
However, KNN materials exhibit a relatively high dielectric loss (tan δ) and insufficient durability. This problem exists not only in liquid ejecting heads represented by an ink jet recording head, but also in piezoelectric elements used in other apparatuses.